pcmhacking.net

no point lifting the valve higher than where the heads flow the most it just adds wear and tear for no gains.

The1 wrote:XP Hot cam seemed to be all the rage with L67's for a long time, ZZP is where to get them, mace sell them also. But cause of the lift id say is why they require going back to stock ratio rockers?

http://shop.zzperformance.com/store/c/4 ... train.aspx

I was reading up a post here which put the question in my head about keeping the YT 1.95 rockers and going custom grind.
http://l67torque.net/viewtopic.php?p=80444#p80444

Stock heads are good for .515" lift before you have trouble with valve guide seal and valve spring retainer clearance issues. The MACE Manley retainers are machined to give you another .030 clearance and if you also use the MACE viton seal you gain another .020 clearance. These used with the correct springs now give you .565" lift. If you want more total lift you will need to machine down the valve guides and combined with the #105 or #130 springs are good for .600" lift.

What Delco said also has merit. I'll try and track down a flow chart for a ecotec/l67 head to see if we can get some numbers.

yeh the idea would be more duration? the rockers are doing the lift, dont want anything extreme, may as well reuse them and custom grind isn't high cost over shelf cam, on my N/A i have those retainers from memory and viton seals. The stock stall on L67 Converter is 2300rpm i think.

This link has some head flow numbers,

http://www.abbottracingheads.com/gm3800.htm

If the numbers are accurate it would indicate that these heads do flow well right up .600" lift

you can see they start to run out after 500 2 cfm isnt worth straining everything for

looks to be diminishing gains past .500" though? I think 1.95 rockers from what i can find give about that with stock cam.

Would be a different kettle of fish with boost though. If your running roller tipped rockers you shouldn't have to much of a problem with valve guide wear either.

I'd imagine that a cam/rocker combination with about .500" - .550" total lift would probably be ideal for performance and reliability.

Stock cam with 1.95:1 rockers would see you at about .500" lift.

XP hot cam ( same as MACE stage 2 I think) has .520" in/.536" ex with stock 1.6 rockers.

someone fitted mace 1.98 rockers and 105lb springs the other day to an l67 for a massive gain of 9hp LOL thats an expensive 9hp

i saw that, must have been a crap tune or something cause i made 11hp

well zzp emailed me back and said they've never done a cam to suit rockers.

Crow Cams ive found has these but only seems to be on the mace site.
http://www.maceengineering.com.au/epage ... cts/CAM607

Havn't heard from anyone else yet.

There's always the option of using stock setup and selling the rockers, which i guess then opens up freedom to get any grind.